Conventionally, it is known to mount an electronic part such as a connector on an electric circuit board, by pushing a holding member attached to the electronic part into a through hole formed in the electric circuit board. Further, there is a case in which the holding member is soldered to the electric circuit board in order to firmly fix the electronic part to the electric circuit board.
As such a holding member, there is proposed, for example, a technique for pushing a flat holding member, which is formed by stamping a metal plate, into a through hole of an electric circuit board, by elastically deforming the holding member in an in-plane direction (see, for example, Japanese Utility Model Laid-Open No. H6-62486 and U.S. Pat. No. 5,529,514). This holding member has such a shape that hook sections are positioned at both external sides of a pair of leg sections, which extend like a fork from a head section. The head section is fixed to a connector.
When the leg sections of the holding member are pushed into a through hole of an electric circuit board, the hook sections are caught on the electric circuit board after passing through the through hole of the electric circuit board. Therefore, even when the holding member fixed to the connector is in a state of being merely pushed into the through hole and yet to be soldered, the connector is retained not to fall off the electric circuit board by the holding member. However, since this holding member is flat and the pair of leg sections are made to elastically deform only in the in-plane direction, a large force is required to cause elastic deformation. Furthermore, the spring constant is difficult to reduce as compared to a spring capable of being elastically displaced in a board thickness direction. In addition, the amount of elastic deformation is small and a range in which plastic deformation is not achieved yet is limited. For this reason, there is a possibility that a notch in the surface of each of the pair of leg sections, which are formed by subjecting a metal plate to stamping, may make strong contact with an inner surface of the through hole when being pushed in, thereby damaging the inner surface of the through hole.
As a result, a known holding member addresses such a problem. For example, this holding member includes a pair of leg sections that extend in the approximately same direction from a tabular base section fixed to a connector, have respective wide-width spring pieces capable of being elastically displaced in a board thickness direction, and face each other (see, for example, Japanese Patent Laid-Open No. 2007-128772). The pair of leg sections of this holding member elastically deform in the board thickness direction, when this holding member is pushed into the through hole. Furthermore, when the holding member is merely pushed into the through hole and yet to be soldered, the holding member is held without falling off the electric circuit board since outer surfaces of the pair of leg sections are contact with an inner surface of the through hole. According to this design, when the holding member is pushed into the through hole, the outer surfaces of the pair of leg sections make soft contact with the inner surface of the through hole, which prevents the inner surface of the through hole from being damaged. However, this holding member has a disadvantage in that it is difficult to increase the elasticity of the leg sections. Therefore, such a holding member has a low holding strength in the state in which the holding member is merely pushed into the through hole and yet to be soldered. For this reason, for example, when the connector is grasped and handled by a robot while the holding member is in such a state, or when the holding member in such a state is pulled hard, the leg sections of the holding member may come out of the through hole.